1. Field of the Invention
The invention relates to a method of cleaning semi-conductor materials, and more particularly to a method of cleaning copper material surfaces in ultra large scale integrated circuits (hereinbelow refer to as ULSI) after polishing the surfaces.
2. Descriptions of the Related Art
The increase in the density of integrated circuits and the decrease in the size of elements thereof make the capacity between wires and the resistance of metal interconnects enlarge, which results in longer resistance and capacitance delay (RC delay). Copper has a low resistivity and thermal sensitivity, and superb anti-electromigration; in addition, it produces a shorter RC delay and improves the reliability of circuits. Thus, copper wire is an ideal substitute for aluminum wire to work as interconnection lines.
Chemical-mechanical polishing (hereinbelow refer to as CMP) for copper in ULSI has been one of the focused core technologies of the world. Currently, when the polishing process of the CMP method is accomplished, molecular bonds of surface atoms of copper are just broken, so that the surface has a high energy which can easily adsorb small grains to lower the surface energy. Therefore, grains of abrasive in the polishing solution are very easy to be adsorbed on copper surface; residues of polishing solution surrounding grains have large surface tension, and are distributed as globules on copper surface, which easily results in uneven corrosion, bad surface uniformity, increase in the later cleaning cost, and decrease in product yields.